Changes in plant community diversity and aboveground biomass along with altitude within an alpine meadow on the Three-River source region

The grassland is an important component of terrestrial ecosystems and plays a significant role in biodiversity and ecosystem functions. In the present study, the changes of plant species diversity and aboveground biomass productivity were examined along with the altitude in natural alpine grassland in the source region of three rivers on the Qinghai-Tibetan Plateau. Eleven experimental locations were selected with altitudes ranging from 3862 to 4450 m above sea level (a.s.l.). The results indicated that Kobresia pygmaea meadow, Kobresia humilis meadow and Salix cupularis shrub meadow had higher indices of diversity and aboveground biomass. The distribution of species diversity, richness and aboveground biomass showed similarly unimodal patterns across the altitude gradient with the highest indices appeared at mid-altitudes locations. The changing trend of species diversity, richness and evenness also showed significant unimodal patterns with total aboveground biomass, and the highest species diversity occurred at intermediate level of productivities. This research would provide a valuable reference for the protection of grassland biodiversity and maintaining of the grazing ecosystem function in the source region of the Three Rivers.